Need to Register?

jmcwilliams2003 · October 4th, 2009

Many people have advised me to create a thicker stencil on my screens in order to lay down a nice white underbase. I have pretty much all the other techniques down, but i would like a thicker stencil in order to help me with a smoother base. I have some luck, but with things like sweatshirts and sweatpants i get too many fibers sticking up which makes for bad looking colors on top of the white.

I have tried to use the smooth side of the scooper and it looks to work well. Yet, the emulsion either doesnt wash out or completely washes out. According to the directions for my emulsion, you are only supposed to use a 1/1 thin coating using the sharp side otherwise these things can happen. I am using:

Kiwocol Poly-Plus Z emulsion.

I have used 2/2 on the smooth side and let dry for long periods of time. The emulsion ends up sticky and sometimes ruins the films and sticks to the glass. I am starting to believe that the emulsion I use simply is not made to use as a thick coating.

Can anyone recommend an emulsion that i could use for my 110-156 screens that can put on a thick coating for a nice underbase?

Thanks!

Jason

out da box · October 4th, 2009

Try Qtx or chroma blue.

RichardGreaves · October 4th, 2009

A thin smooth print on the surface of your shirt results in the best print. This is the reason heat transfers make the best white prints. All the ink that is driven into the shirt reduces the film on the surface. Low mesh tension is the most common reason for poor images on dark shirts.

Use the mesh to meter the ink deposit.
Use a thin stencil to contain the ink and shape the print.

Thick white ink (and all heavily pigmented special effects inks), should be tested with 83 mesh woven with 70 micron threads. Large open area because of the thin threads.

Too often we are forced to print large logos that are flat white images that were not designed for dark textiles. My nightmares are filled with NY Yankees & Marlboro logos.

Higher tension, and a stiff sharp blade to overcome the high tension off-contact distance, are the most rewarding principles to follow.

Emulsions with higher solids content shrink less as the water evaporates.

Start coating on the bottom of the screen until you see the emulsion link up on the other side and form a shiny gloss coating. Now you know you have at least filled the mesh holes.

If you don't fill the holes, when you turn the frame and make final, layering coats from the inside of the screen, air will get trapped in the holes that are now like bubbles, reducing the amount of emulsion in the holes as the water evaporates.

RichardGreaves · October 4th, 2009

Quote:

Originally Posted by jmcwilliams2003


	Yet, the emulsion either doesnt wash out or completely washes out. I have used 2/2 on the smooth side and let dry for long periods of time. The emulsion ends up sticky and sometimes ruins the films and sticks to the glass.

The coating section of the Poly Plus Z Technical Information sheet reads:

Coating can be done manually or by machine. The use of the KIWOMAT coating machine is especially recommended because it achieves a reproducible coating result. If coating is done manually ensure that the mesh openings are filled from the substrate side (generally 2-3 coats).

Only then begin with the emulsion build-up from the squeegee side (1-3 coats) depending on the print requirements.

KIWOCOL POLY PLUS Z’s high solids content offers rapid build with few coats, fast drying, and smooth stencils

In the Guide values section:
The following approximate exposure times were established using a 5,000 Watt metal halide lamp at a distance of 40 inches and coating with a round edged coating trough twice from the substrate side followed by twice from the squeegee side (2-2).

Measuring Exposure
2/2 is much thicker than 1/1, so you will need more exposure so the UV energy can move all the way through the stencil to the inside of the stencil, to cure it.

When you are tired of guessing about exposure, purchase a Stouffer 21 Step Sensitivity Guide US$10.00 to US$12.00 depending on where you buy it. It will give you visual feedback and should be on every screen your make for the rest of your life.

Exposure or Emulsion????? (http://www.t-shirtforums.com/t24239.html#post143704)
Exposure FAQ of Screen Making Products (http://www.ulano.com/FAQ/FAQexposure.htm#Q1)

Stencils are easy.

Stencil doesn't stay in the mesh
If the stencil washes out - it wasn't exposed with enough UV-A energy, so it dissolves with water and rinses down the drain; just like it is supposed to.

Image area doesn't wash out
If the image area doesn't wash out, it was somehow cross-linked with heat or UV-A energy, this usually means your positive failed to stop UV energy from reaching the stencil.

Dime Complete Opacity Test
To judge if your positive completely stops UV energy, tape a dime or a piece of aluminum foil to the stencil to see if the dark areas of your positive are failing you and letting UV-A energy through to the stencil. If the area covered by the dime doesn't wash out, you have exposed the stencil to UV energy or heat energy when you dried & stored it and the stencil resists dissolving with water and going down the drain.

jsf · October 4th, 2009

I agree with Greaves.

I normally coat my screens with 1/1. The thinner the better. For halftone process.

Should the design be solid colors, then 1/2 coats is just enough... If you need a thicker ink deposit "do not" thicken you emulsion coats just use meshes 80-100. These will give you thicker ink deposit.

One problem when applied thicker coats of emulsion to your screen is ink build-up that may cause undesired print result.

alan802 · October 5th, 2009

I think the problem is that most people don't know what the proper emulsion over mesh (correct stencil thickness) feels like. A 1/1 coating with a 45% solids emulsion on a 156 screen yeilded a less than desirable stencil for us, about 15% eom. When we coated with a 1/1 or 1/2 our stencils are too thin and our print has no sharpness to the edges and does not suit my eye. You have to have some edge to the stencil to keep the edges of your print sharp. We don't coat anything less than 2/2 and all of our stencils range in the 20-35% Emulsion over Mesh. I have printed the same mesh screens that were coated differently side by side and comparing a 2/2 to a 1/1 coat were drastically different. I'm not saying a 3/3 or more would be better but there is a "window" that we try to reach with our stencils that produce the best looking print, and they are not with a 1/1 coat. You can get away with very thin stencils on alot of applications and it will work most of the time. We have many jobs that are complex on darks that I need as close to perfect stencils to make the print look good so we choose to coat all of our screens to meet the 20-30% eom.

When setting up our coating techniques for the different mesh counts, we used Richard's method of coating the shirt side until the emulsion encapsulates the mesh on the other side, then coat at least two on the squeegee side and that gave us the right ratio of eom that most emulsion companies say to use. We are on the high side of that 20-30% over the entire range of mesh counts. The Greaves method of coating will put you in that range without having to invest in a thickness gauge.

alan802 · October 5th, 2009

Jason, we have issues with the film sticking to the emulsion after exposure and it ruins the film. It happens to us on our lower mesh counts where there is more emulsion on the screen and nothing we have done to our dark room or techniques have made it better. We even switched emulsions, bought a hygrometer to see if our dehumidifier was working correctly and talked to the emulsion tech's over the phone. The only thing that works is a little bit of baby powder on the screen before you tape the film. It doesn't solve the problem, but it will save your film.

Need to Register?

Resources

T-Shirt Sites

Correct Emulsion for thick stencil for white ink?